title: Synthesis and Characterization of Hydrido Carbonyl Molybdenum and Tungsten PNP Pincer Complexes.
abstract: In the present study the Mo(0) and W(0) complexes [M(PNP)(CO)3] as well as seven-coordinate cationic hydridocarbonyl Mo(II) and W(II) complexes of the type [M(PNP)(CO)3H]+, featuring PNP pincer ligands based on 2,6-diaminopyridine, have been prepared and fully characterized. The synthesis of Mo(0) complexes [Mo(PNP)(CO)3] was accomplished by treatment of [Mo(CO)3(CH3CN)3] with the respective PNP ligands. The analogous W(0) complexes were prepared by reduction of the bromocarbonyl complexes [W(PNP)(CO)3Br]+with NaHg. These intermediates were obtained from the known dinuclear complex [W(CO)4(μ-Br)Br]2, prepared in situ from W(CO)6and stoichiometric amounts of Br2. Addition of HBF4to [M(PNP)(CO)3] resulted in clean protonation at the molybdenum and tungsten centers to generate the Mo(II) and W(II) hydride complexes [M(PNP)(CO)3H]+. The protonation is fully reversible, and upon addition of NEt3as base the Mo(0) and W(0) complexes [M(PNP)(CO)3] are regenerated quantitatively. All heptacoordinate complexes exhibit fluxional behavior in solution. The mechanism of the dynamic process of the hydrido carbonyl complexes was investigated by means of DFT calculations, revealing that it occurs in a single step. The structures of representative complexes were determined by X-ray single-crystal analyses.
authors.affiliation: Institute of Applied Synthetic Chemistry, Institute of Materials Chemistry, and Institute of Chemical Technologies and Analytics, Vienna University of Technology , Getreidemarkt 9, A-1060 Vienna, Austria.
authors.forename: Ozgür
authors.initials: O
authors.lastname: Oztopcu
authors.forename: Christian
authors.initials: C
authors.lastname: Holzhacker
authors.forename: Michael
authors.initials: M
authors.lastname: Puchberger
authors.forename: Matthias
authors.initials: M
authors.lastname: Weil
authors.forename: Kurt
authors.initials: K
authors.lastname: Mereiter
authors.forename: Luis F
authors.initials: LF
authors.lastname: Veiros
authors.forename: Karl
authors.initials: K
authors.lastname: Kirchner